Method for fabricating periodically multilayered film

Abstract

A method for fabricating a periodically multilayered film having a plurality of amorphous thin layers of different kinds stacked periodically is performed by forming at least one kind of the layers in the stack by a photo CVD method, whereby a more definite periodicity in the composition of the lattice and fewer defects are achieved.

What is claimed is: 
     
       1. A method for fabricating a periodically multilayered film having a plurality of amorphous thin layers of different kinds stacked periodically to form a stack, comprising the step of assuring a more definite periodicity in the composition of said stack by forming at least one type of said layers in said stack by photo CVD, whereby defects in the stack are reduced. 
     
     
       2. The method of claim 1, wherein different types of said layers are formed in the respective reaction chambers. 
     
     
       3. The method of claim 2, wherein all types of said layers are formed by photo CVD. 
     
     
       4. The method of claim 2, wherein one type of said layers is formed by plasma CVD. 
     
     
       5. The method of claim 2, wherein one type of said layers is formed by thermal CVD. 
     
     
       6. The method of claim 1, wherein different types of said layers differ from one another in at least one band gap and conductivity type. 
     
     
       7. The method of claim 6, wherein said periodically multilayered film comprises substantially i-type hydrogenated amorphous silicon carbide layers and p-type hydrogenated amorphous silicon layers. 
     
     
       8. The method of claim 6, wherein said periodically multilayered film comprises substantially i-type hydrogenated amorphous silicon layers and p-type hydrogenated amorphous silicon carbide layers. 
     
     
       9. The method of claim 1, wherein said layers contain at least one of the elements of group IVa of the periodic table. 
     
     
       10. The method of claim 9, wherein said periodically multilayered film has an energy band gap which changes periodically in the direction of the thickness. 
     
     
       11. The method of claim 10, wherein one type of said layers having the larger band gap comprises at least one element selected from the group consisting of silicon, silicon carbide, silicon nitride, silicon oxide and carbon. 
     
     
       12. The method of claim 10, wherein the other type of layers having the smaller band gap comprises at least one element selected from the group consisting of silicon, silicon germanium, silicon tin and germanium.